Pen



FIG. 1 is a front perspective view of my new design for a pen;

FIG. 2 is side view in elevation of the new design showing the device inverted;

FIG. 3 is a side perspective view of the new design;

FIG. 4 is a top view depicting the point of the pen;

FIG. 5 is a bottom view of the new design; and,

FIG. 6 is side view in elevation of the new design. 

The ornamental design for a pen, as shown and described. 